ARM: dts: omap4-panda: Add I2c pinctrl data

Booting 3.8-rc6 on omap4 panda results in the following error

[    0.444427] omap_i2c 48070000.i2c: did not get pins for i2c error: -19
[    0.445770] omap_i2c 48070000.i2c: bus 0 rev0.11 at 400 kHz
[    0.473937] omap_i2c 48072000.i2c: did not get pins for i2c error: -19
[    0.474670] omap_i2c 48072000.i2c: bus 1 rev0.11 at 400 kHz
[    0.474822] omap_i2c 48060000.i2c: did not get pins for i2c error: -19
[    0.476379] omap_i2c 48060000.i2c: bus 2 rev0.11 at 100 kHz
[    0.477294] omap_i2c 48350000.i2c: did not get pins for i2c error: -19
[    0.477996] omap_i2c 48350000.i2c: bus 3 rev0.11 at 400 kHz
[    0.483398] Switching to clocksource 32k_counter

This happens because omap4 panda dts file is not adapted to use i2c through
pinctrl framework. Populating i2c pinctrl data to get rid of the error.

Tested on omap4460 panda with 3.8-rc6 kernel.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
Reported-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>